The packet switch data service is a very important service of 3GPP2. The advanced functions, such as accessing the network in mobile environment, can be achieved for users. Because the data switch of the service does not go through the Mobile Switch Center (MSC) and the Service Control Point (SCP), its speed exceeds the limitation, 64 k, of the conventional time-gap switch. In the data packet switch service, the data transmission bypasses the switch center. The Mobile Station (MS) exchanges the data with Packet Data Service Network (PDSN) directly through the Base Station Center (BSC) and the Packet Control Function (PCF). The MSC and SCP only authorize the user, i.e. the MSC and SCP only check whether the user is allowed to use the data service and whether the balance in the account is enough for continuing the calling function. However, the data stream of data service goes through the path, MS<->BSC<->PCF<->PDSN.
After CDMA mobile switch uses the 3G1x packet switch data service, the billing of the service bypasses the MSC calling control layer, therefore, billing can only be implemented by the PCF. In the PCF, there are currently two billing methods, by amount of data and post service. None of them are real time billing methods. They might be suitable for the normal CDMA users, but not suitable for the IN prepaid users. Because the balance on the account of the IN prepaid users are stored on the SCP, the PCF cannot charge the users in real time. Therefore, the current network architecture of the packet switch data service is not suitable for billing the prepaid user. Otherwise, it is very likely to cause deficits on the accounts, which will lead to loss for carriers and end users. However, IN service and data service are indeed the star services with competitive strength in the CDMA market, and the difficulty of unifying the method of billing for the two services will block the development of CDMA data services.